The present invention generally relates to the field of pipe assemblies such as those used in vehicular exhaust systems and more particularly to an assembly having corrugated conduits that are clamped onto rigid piping and utilize a metal seal element to provide a fluid-tight connection therebetween. The present invention further provides a system that minimizes possible damage to the corrugations of the conduit.
Conduit and piping systems for conveying fluids and bulk materials are used in a wide variety of applications. Various components for such systems have been devised to accommodate different fluids and materials and to operate in particular environments. For example, some of the components of such systems are fabricated from flexible metal hose, which offers the advantages of durability, flexibility, relatively low cost and adaptability to various sizes, configurations and materials.
Flexible metal hose has been used for many years to interconnect components which move relative to each other. Some of the common configurations of flexible metal hose include spiral-wound, edge-interlocked hose wherein the edges of a strip of sheet metal are interlocked on a hose winding machine to permit limited deflection of the resulting flexible metal hose.
Corrugated flexible metal hose is another type of hose that can be, used. The corrugations provide flexibility and permit a corrugated pipe or hose section to be bent and shaped more easily than a comparable hose section with smooth walls. Moreover, corrugations can dissipate dynamic stresses associated with the vibration of the components to which the flexible hose section is attached.
Corrugated flexible hose sections can have corrugations of different diameters, such as bellows-type arrangement with the largest-diameter corrugations in the center and corrugations of decreasing diameters toward the ends whereby maximum flexibility is achieved in the center with increasing stiffness toward the ends (see U.S. Pat. No. 5,769,463 to Thomas). Such bellows-type configurations tend to be relatively efficient at dissipating vibrational energy toward their centers.
Hybrid flexible metal hose sections have also been fabricated from corrugated sheet metal bands which are spiral wound with their edges interlocked. The resulting hose sections can provide the advantages of both interlocked-edge and corrugated types of flexible metal hose types. For example, see Thomas U.S. Pat. No. 5,494,319.
Exhaust systems for internal combustion engines are examples of relatively severe environments in which the operating characteristics of flexible metal hoses can be used to advantage. Flexible metal hose sections are often used for connecting exhaust pipes from vehicle internal combustion engines with manifold mufflers, tail pipes and other exhaust system components. Flexible metal hose sections are commonly used in exhaust systems of tractors of tractor-trailer truck rigs and off road and construction vehicles because of their flexibility, temperature resistance and corrosion resistance when fabricated from suitable materials, such as stainless steel, galvanized steel or other metals.
Exhaust systems in general and vehicle exhaust systems in particular must perform reliably under relatively severe operating conditions, which can include temperature extremes, corrosive environmental factors and dynamic stress loading. Dynamic stresses in an exhaust system can originate from vibrations associated with the engine and movement of the vehicle. Such dynamic stresses include axial, lateral and angular forces, all of which can normally be effectively attenuated and controlled by flexible metal hose with corrugations and/or edge interlocking. However, torsional forces caused by the differential rotation of the exhaust system components connected by a flexible metal hose section can inflict significant damage, particularly when the flexible hose section ends are fixedly secured and the flexible section design is rigid with respect to rotational forces. Such dynamic torsional forces can lead to premature metal fatigue, cracking and failure of exhaust system components, including previous designs of flexible metal hose.
Pending U.S. patent application Ser. No. 10/718,785 filed by Thomas on Nov. 21, 2003 and published on May 27, 2004 discloses a system that effectively addresses the problem of dynamic torsional forces. Mating corrugations on corrugated conduits interfit so that the conduits can rotate relative to one another while maintaining a seal. While this system has worked well, it is not wholly without problems.
Notably, the corrugated pipe has an inside diameter greater than the outside diameter of the upstream pipe to which it is connected. A pipe clamp can be tightened on this joint to connect the piping components. However, the corrugated pipe is crushed and crumpled in the process because of its initially loose fit, thus leading to leakage at this joint. This is a serious problem and even more serious in the case of a system of the type shown in the pending Thomas application because crushing of the corrugated pipe can result in deformation extending to the corrugations. If that happens, the corrugations can be damaged to the point where relative rotation of the corrugated pipes is impeded or prevented altogether, thus resulting in failure of the system.
Another problem is that the clamp can slide on the pipe and possibly bang into and damage the corrugations as the clamp is being applied. This damage can lead to the same unacceptable result.